ABSTRACT The proposed research will enhance cancer care for the ~75,000 women diagnosed with cancer at reproductive ages each year by providing contemporary evidence on fertility preservation outcomes. Accepted, non-experimental preservation options are limited to embryo and oocyte cryopreservation, both of which ultimately require in vitro fertilization (IVF) to achieve pregnancy. Fertility preservation counseling has been recommended by national cancer care guidelines for over a decade; however, there is inadequate evidence to allow patients and their providers to make informed decisions. In non-oncologic settings, IVF success rates range from 45% to 11% from the youngest to the oldest women. Our preliminary analyses and other studies suggest that response to IVF treatment may be worse among women with a cancer history. To address this evidence gap, we propose using detailed IVF data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS), a national IVF database that includes >90% of IVF procedures since 2004, linked to State cancer registries and vital records (birth certificates) in 14 States. This proposed project will expand our pilot study in 3 States to 14 States to form a cohort of >663,000 U.S. women who had IVF cycles during 2004-16 and contribute close to five million person-years of follow-up. The study population will include an estimated 13,000 women with a cancer history, followed for up to 13 years after diagnosis. Within this cohort, we will 1.) Compare IVF cycle outcomes (oocytes retrieved, % of embryos that survive freeze/thaw, conception rates, and # of cycles required for conception) between three groups: those who initiate IVF before cancer treatment; after cancer treatment; and without a cancer history. We will also 2.) Compare IVF live birth rates and outcomes (length of gestation, birthweight, fetal growth restriction, gestational hypertension, and congenital malformations) in the three groups. Finally, we will 3.) Investigate the association between storage time of cryopreserved oocytes or embryos and IVF conception and live birth rates for women who return for thawing oocytes or embryos; and evaluate rates of spontaneous conception (i.e., live births without embryo transfer) for those who do not return. The proposed research is ideally timed to evaluate newly-accepted oocyte cryopreservation and dissemination of random-start IVF protocols to reduce the potential for cancer treatment delays. The research will provide a critical evidence base to women who must make time sensitive decisions about fertility preservation while faced with a potentially life threatening and financially devastating cancer diagnosis.